INTERNET-DRAFT H. Kitamura
NEC Corporation
Expires in six months A. Jinzaki
S. Kobayashi
Fujitsu Laboratories LTD.
19 April 1999
A SOCKS-based IPv6/IPv4 Gateway Mechanism
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document describes an IPv6/IPv4 gateway mechanism that is based
on the SOCKS protocol [SOCKSv5]. By enhancing the SOCKS mechanism to
support the heterogeneous communications relays between IPv6 and IPv4
at the SOCKS server, the SOCKS-based IPv6/IPv4 gateway mechanism is
accomplished.
The SOCKS-based gateway mechanism enables the IPv6 nodes and IPv4
nodes to communicate with each other smoothly without sacrificing any
conveniences and functionalities of current communication methods.
H. Kitamura et al. [Page 1]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
1. Introduction
This document describes an IPv6/IPv4 gateway mechanism that is based
on the SOCKS protocol [SOCKSv5]. By enhancing the SOCKS mechanism to
support heterogeneous communications, the SOCKS-based IPv6/IPv4
gateway mechanism is accomplished.
The SOCKS-based gateway mechanism is designed to satisfy the
following requirements.
1. Maintain the conveniences of current IPv4 communication methods
and frameworks of existing communication networks
2. Utilize existing user applications that are designed only for IPv4
communications to heterogeneous communications without modifying
them.
2. Be scalable and able to support the translations for all typical
communication services.
Since the SOCKS-based IPv6/IPv4 gateway mechanism is based on
relaying two "terminated" connections, most problems of the NAT-based
translator mechanisms are eliminated.
Another advantage of the mechanism is that there is no need to modify
the DNS system, because it has a mechanism that enable the DNS name
resolving actions of SOCKS clients to be delegated to an enhanced
SOCKS server that has both IPv6 and IPv4 stacks.
This DNS name resolving delegation mechanism is realized by modifying
(socksifying) client applications. This is a constraint. To eliminate
the need to modify the DNS system, it is necessary to socksify the
applications. Thus, there is a dilemma in that either socksification
or DNS modification is necessary.
Also, the mechanism has the following additional by-product benefits.
Since the SOCKS-based gateway mechanism has much flexibility, it can
support various topologies that mix IPv4 and IPv6 communications. In
case of multiple chained relay topologies, the SOCKS-based gateway
mechanism can realize similar topologies that are supported by packet
tunneling techniques. Compared with other translator mechanisms, the
SOCKS-based gateway mechanism has the following benefits. There is no
packet fragmentation vulnerability, and the connection can be
authenticated by the native SOCKS authentication methods.
2. Basic SOCKS-based Gateway Mechanism
The Fig. 1 shows the basic SOCKS-based gateway mechanism.
H. Kitamura et al. [Page 2]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
Client C Gateway G Destination D
+-----------+ (Server)
|Application|
+-->+===========+ +-------------+ +-----------+
same-+ |*SOCKS Lib*| | *Gateway* | |Application|
API +-->+===========+ +=====---=====+ +-----------+
| Socket DNS| | Socket DNS | | Socket DNS|
+-----------+ +-------------+ +-----------+
| [ IPv X ] | |[IPvX]|(IPvY)| | ( IPv Y ) |
+-----------+ +-------------+ +-----------+
|Network I/F| | Network I/F | |Network I/F|
+-----+-----+ +---+-----+---+ +-----+-----+
| | | |
+============+ +------------+
socksified normal
connection connection
(ctrl)+data data only
Fig. 1 Basic SOCKS-based Gateway Mechanism
In this figure, the Client C initiates the communication to the
Destination D. Two new functional blocks that compose the system are
introduced.
One, *Socks Lib*, is introduced into the client side (Client C) (this
procedure is called "socksifying"). It is located between application
layer and socket layer, and can replace applications' socket APIs and
DNS name resolving APIs (e.g., gethostbyname(), getaddrinfo() etc.)
dynamically. A mapping management table exists in it for "DNS name
resolving delegation" mechanism (described below). Each socksified
application has its own *Socks Lib*.
The other, *Gateway*, is an enhanced SOCKS server. It is installed on
the IPv6 and IPv4 dual stack node (Gateway G). All types of protocol
combinations are relayed there between Client C (IPvX) and
Destination D (IPvY). The *Socks Lib* invokes it. Each *Gateway*
takes charge of one socksified connection.
H. Kitamura et al. [Page 3]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
The following four types of combinations of IPvX and IPvY are
possible in this mechanism.
type C ------ G ------ D
[IPvX] (IPvY)
A IPv4 IPv4 homogeneous (normal SOCKS)
B IPv4 IPv6 * heterogeneous *
C IPv6 IPv4 * heterogeneous *
D IPv6 IPv6 homogeneous
Type A is supported by the normal SOCKS mechanism. Type B and C are
the main targets for the SOCKS-based gateway mechanism. They provide
heterogeneous communication topologies. Type D can be supported by
the natural extension of the SOCKS mechanism, because it is a
homogeneous communication.
The *Socks Lib* communicates with the *Gateway* by using SOCKS
protocol [SOCKSv5]. The connection between the Client C and the
Gateway G is called a "socksified connection." It can transfer not
only data but also control information (e.g. location information of
the Destination, etc.).
In order to provide appropriate destination information to the
application on the Client C, the *Socks Lib* also replaces other
types of socket APIs (e.g., getpeername(), etc.) that provide
information about the destination, and necessary information for this
replacement is transferred via the socksified connection. This
mechanism provides the same usability of current communication
methods to the applications on the Client C, and it is not necessary
to modify the applications at all to utilize this mechanism.
The connection between the Gateway G and the Destination D is an
ordinary connection. Server applications on Destination D understand
that the source of the connection is the Gateway G (not Client C). It
is not necessary to modify (socksify) them.
3. DNS Name Resolving Procedure
As [TRANSMECH] mentioned, it is essential for the transition
mechanisms to cooperate with the DNS name resolving mechanism. The
SOCKS-based gateway mechanism has the capability to cooperate with it
without modifying the DNS system. This function is one of the big
advantages of the SOCKS-based gateway mechanism.
In this section, the procedure of how the SOCKS-based gateway
mechanism cooperate with the DNS name resolving mechanism is
described.
H. Kitamura et al. [Page 4]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
1. An application on the source terminal (Client C) tries to get the
IP address information of the destination terminal (Destination D) by
calling the DNS name resolving function (e.g., gethostbyname2()). At
this time, the logical host name ("FQDN") information of the
Destination D is passed to the *Socks Lib* as an argument of called
APIs.
2. Since the *Socks Lib* has replaced such DNS name resolving APIs,
the real DNS name resolving APIs is not called here. The argued
"FQDN" information is merely registered into a mapping management
table of *Socks Lib*, and a "fake IP" address is selected as a reply
value from a reserved special IP address space that is never used in
real communications. The "fake IP" address must be suitable for
requests called by the applications. Namely, it must belong to the
same address family of the Client C, even if the address family of
the Destination D is different from it. After the selected "fake IP"
address is registered into the mapping management table as a pair
with the "FQDN", it is replied to the application.
3. The application receives the "fake IP" address, and prepares a
socket. The "fake IP" address information is used as an element of
the "socket". The application calls socket APIs (e.g., connect()) to
start a communication. The "socket" is used as an argument of them.
4. Since the *Socks Lib* has replaced such socket APIs, the real
socket function is not called. The IP address information of the
argued socket is checked. If the address belongs to the special
address space for the fake address, the matched registered "FQDN"
information of the "fake IP" address is obtained from the mapping
management table.
5. The "FQDN" information is transferred to the *Gateway* on the
relay server (Gateway G) by using the SOCKS command that is matched
to the called socket APIs. (In case of connect(), the CONNECT command
is used.)
6. Finally, the *Gateway* calls the real DNS name resolving APIs
(e.g., gethostbyname2()). At this time, the received "FQDN"
information is used as an argument of the called APIs.
7. The *Gateway* receives the "real IP" address from a DNS server,
and creates a "socket", The "real IP" address information is used as
an element of the "socket".
8. The *Gateway* calls socket APIs (e.g., connect()) to communicate
with the Destination D. The "socket" is used as an argument of them.
By using this mechanism, DNS name resolving actions are delegated
H. Kitamura et al. [Page 5]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
from the source terminal (Client C) to the relay server (Gateway G).
Thus the mechanism is called "DNS name resolving delegation."
* DNS Name Resolving Delegation and address mapping
The advantages of the "DNS name resolving delegation" mechanism come
from the fact that the DNS name resolving actions are taken at the
relay server (Gateway G). Since the relay server is an IPv4 and IPv6
dual stack node, DNS name resolving queries for any types of
destinations can be done without causing problems. It is not
necessary to modify the existing DNS mechanism at all.
Without this mechanism, an IPv4 application can not resolve the host
name of an IPv6 destination. Even if it can get the IPv6 address by
some method, it is impossible for the IPv4 application to deal with
such an IPv6 address. It is impossible because the IPv6 address is
four times longer than the IPv4 address, and the IPv4 application
does not have any long address space in which to store it.
Using this mechanism brings forth an additional advantage: an IPv4
application can also use a numerical IPv6 address expression to
specify an IPv6 destination terminal. Since the IPv6 address
expression includes colons (":"), it is identified as an FQDN
expression (not a numerical IP expression) for the IPv4 application.
Thus the numerical IPv6 address expression is treated the same as the
DNS expression in the "DNS name resolving delegation" mechanism.
The problem with the mechanism is that a failure of the DNS name
resolving process is detected incorrectly at the source terminal
(Client C). It is detected as a failure of the connection creation.
In order to solve this problem, the author has proposed extensions of
the current SOCKS protocol [SOCKS5EXT].
* Address Translation and Mapping
One of the good characteristics of the SOCKS-based gateway mechanism
is its ability to manage address translation and mapping wisely.
In case of the NAT-based transparent model translator mechanism
(e.g., [NATPT]), it is necessary to reserve global and wide address
space for the address mapping. Also, complex address allocation and
management mechanisms (by introducing address mappers, etc.) are
needed.
In case of the SOCKS-based gateway mechanism, such complex mechanisms
are not necessary, because corresponding address mapping is done at
the *Socks Lib* by using the fake IP address and the mapping
H. Kitamura et al. [Page 6]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
management table. The mapping management table is prepared on each
application. It is locally closed and independent from others.
Therefore, it is easy to manage the table, and it is not necessary to
reserve global and wide address space.
As [CATTRANS] mentioned, the SOCKS-based gateway mechanism is free of
the address mapping problem.
4. Multiple Chained Relay Mechanism (Advanced usage)
The SOCKS-based gateway mechanism has the flexibility to support
multiple chained relay topologies. With the mechanism, IPv4 and IPv6
mixed various communication topologies are realized.
The Fig. 2 shows the structure of the multiple chained relay
mechanism.
Client C Gateway G1 Gateway G2 Destination D
+-----------+ (Server 1) (Server 2)
|Application|
+===========+ +-------------+ +-------------+ +-----------+
|*SOCKS Lib*| | *Gateway1* | | *Gateway2* | |Application|
+===========+ +=====---=====+ +=====---=====+ +-----------+
| Socket DNS| | Socket DNS | | Socket DNS | | Socket DNS|
+-----------+ +-------------+ +-------------+ +-----------+
| [ IPv X ] | |[IPvX]|(IPvY)| |(IPvY)|{IPvZ}| | { IPv Z } |
+-----------+ +-------------+ +-------------+ +-----------+
|Network I/F| | Network I/F | | Network I/F | |Network I/F|
+-----+-----+ +---+-----+---+ +---+-----+---+ +-----+-----+
| | | | | |
+============+ +==========+ +------------+
socksified socksified normal
connection connection connection
(ctrl)+data (ctrl)+data data only
Fig. 2 Multiple Chained Relay Mechanism
In this figure, the source terminal (Client C) initiates the
communication with the destination (Destination D). Underneath, the
connection is replaced with three connections, and they are relayed
at the two relay servers (Gateway G1 and G2). The *Gateway* includes
the same type of the functions of *Socks Lib*. By enabling the *Socks
Lib* functions at the *Gateway1* on the first relay server (Gateway
G1), the multiple chained relay topology is realized
There is no limitation on the number of relay operations between the
H. Kitamura et al. [Page 7]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
source terminal and the destination terminal. It is possible to have
more than two intermediate relay servers. To simplify the
explanation, twice-relayed topology is shown here. All types of the
protocol relay combinations are possible.
In case of twice-relayed topology, the following eight types of
combinations of IPvX, IPvY, and IPvZ are possible.
type C ------ G1 ------ G2 ------ D
[IPvX] (IPvY) {IPvZ}
E IPv4 IPv4 IPv4 homogeneous (normal SOCKS)
F IPv4 IPv4 IPv6 * heterogeneous *
G IPv4 IPv6 IPv4 * heterogeneous * (tunnel-like)
H IPv4 IPv6 IPv6 * heterogeneous *
I IPv6 IPv4 IPv4 * heterogeneous *
J IPv6 IPv4 IPv6 * heterogeneous * (tunnel-like)
K IPv6 IPv6 IPv4 * heterogeneous *
L IPv6 IPv6 IPv6 homogeneous
Type E is supported by the normal SOCKS mechanism. The types from F
to K are the main targets for the gateway mechanisms. They provide
heterogeneous communication topologies. Type L can be supported by
the natural extension of the SOCKS mechanism, because it is a
homogeneous communication.
Type G and type J can provide interesting topology cases. They are
similar to the topologies that the tunneling techniques can provide.
Compared with the tunneling techniques, the SOCKS-based gateway is
advantageous, because it is composed of relays of real socket
connections. This mechanism does not have to suffer from the
following problems that are caused by tunneling techniques.
* Fragmentation vulnerability
The tunneling technique uses the packet encapsulation mechanism. In
the encapsulation mechanism, the packet length is changed because
of the additional header, and it may exceed the MTU of the network.
Thus, the tunneling technique is vulnerable in that the packet
might be fragmented. With the SOCKS-based gateway mechanism, there
is no fragmentation vulnerability because the packet size is
adjusted at the application layer.
As an added advantage, well-authenticated connections are provided.
This is because the SOCKS mechanism is originally designed for
firewall systems, and it has various authentication methods.
H. Kitamura et al. [Page 8]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
5. Characteristics of the SOCKS-based gateway mechanism
In this section, the characteristics of the SOCKS-based gateway
mechanism are summarized.
1. DNS modification is not necessary:
It is not necessary to reserve global and wide address space for
address mapping.
Also, address map servers are not necessary, because there is a
"DNS Name Resolving Delegation" mechanism.
2. Application independent:
If the applications use socket APIs and DNS name resolving APIs,
the gateway mechanism is applied to them, since the mechanism is
realized by replacing these APIs that at the *Socks Lib*.
As most communication programs use these APIs, there is no
application dependency.
(Applications that exchange IP address information with peers are
exceptions)
3. OS and NIC types independent:
Since the *Socks Lib* and the *Gateway* run at the application
layer, the SOCKS-base gateway mechanism runs on any platforms of
either UNIX or Windows OSs, and there is no dependency on the
types of physical NICs.
4. Only an easy socksification procedure is necessary:
It is easy to install the *Socks Lib* (socksify) to the source
terminal, because the dynamic link library technique helps this
procedure.
5. IPv6 new features (e.g., IPSEC) can be utilized easily:
Since connections are first terminated and then relayed at the
*Gateway*, it is easy to enable IPv6 new features on the IPv6
side.
With NAT-based translators, it is impossible to do the same thing.
6. Current existing client SOCKSv5 library can be used:
H. Kitamura et al. [Page 9]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
In case of the IPv4 -> IPv6 relay, the current existing client
SOCKSv5 library that is designed for IPv4 -> IPv4 communication
can be used without modification.
7. Both TCP and UDP relays are possible:
Since the SOCKS protocol supports both TCP and UDP relays, this
mechanism can also relay both TCP and UDP connections.
8. Both IPv4 -> IPv6 and IPv6 -> IPv4 relays are possible:
This mechanism can realize not only the IPv4 -> IPv6 relay but
also the IPv6 -> IPv4 relay with the same method.
9. Multiple chained relays are possible:
Since the mechanism has flexibility, all types of protocol
combinations of multiple chained relays are possible.
10. Can support exceptional applications that exchange IP address
information at the application level:
It is easy for the SOCKS-based gateway mechanism to introduce
special management routines. If such protocols as ftp are known,
the SOCKS-based gateway mechanism can support them by introducing
special protocol translation routines.
(Implementations of the SOCKS-based gateway mechanism have
supported the ftp protocol translation [see Appendix A])
11. Easy load balancing:
Since the *Gateway* is installed as a server, it is easy to
balance the load by supplying multiple servers.
6. Constraints
The SOCKS-based gateway mechanism requests socksification of
applications (install *Socks Lib*) to realize heterogeneous
communications. Though the socksification is not difficult, it is
one of the constraints for users.
The socksification mechanism provides the advantage that the SOCKS-
based gateway mechanism does not require modification of the DNS
system. Thus, there is a dilemma in that either socksification or DNS
modification is necessary.
H. Kitamura et al. [Page 10]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
Other than the socksification, the SOCKS-based gateway mechanism has
the following three types of constraints.
1. Essential constraints:
Constraints are caused by the address length difference between
IPv4 and IPv6.
Functions that request an IP address as one of the return values
(e.g., getpeername() and getsockname() etc.) can not provide the
correct IP address as a return value. However, an appropriate
port value can be provided, because IPv4 and IPv6 use the same
size port space and necessary port information is transferred by
the SOCKS protocol.
From a realistic viewpoint, this is a minor constraint, because
such functions are called in order to get port information (not IP
address information).
2. Limitation of the SOCKS mechanism:
Since the current SOCKS system can not socksify all of the tricky
applications in which extraordinary means are used to create
connections, the SOCKS-based gateway mechanism can not be applied
to them.
3. Constraints to deal with the fake address:
The fake address must be dealt with as a temporary value at the
application; it must not be recorded permanently as a bookmark,
etc. After the application is finished, the fake address
information must be released. Otherwise, problems will happen.
From a realistic viewpoint, this is also a minor constraint,
because most applications record FQDN information instead of fake
addresses.
It is theoretically possible for the SOCKS mechanism to support ICMP
relays, but the current SOCKS mechanism does not. So, the SOCKS-based
gateway mechanism does not support ICMP relays.
However, the reference implementation of the current SOCKS mechanism
support typical ICMP applications (ping and traceroute) by using
different methods. So, the SOCKS-based gateway mechanism can support
ping and traceroute.
(Implementations of the SOCKS-based gateway mechanism have supported
ping and traceroute [see Appendix A])
H. Kitamura et al. [Page 11]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
7. Experiments
We have been testing SOCKS64, one of the SOCKS-based gateway
implementations in many environments. Since July 1998, we have been
running the SOCKS64 server in between the 6bone and the internal
network of Fujitsu Ltd., Japan. Computers in Fujitsu's internal
network already have been "socksified", so users can connect to 6bone
hosts merely selecting our SOCKS64 server as their SOCKS gateway.
For an interoperability test, we have been providing a SOCKS64 server
in the WIDE Project[WIDEV6WG] Camp, where about 200 Internet
researchers are participating in the camp. A temporary network called
"camp-net" is constructed at the camp for a variety of experiments
and provides services to the attendees. More than a hundred hosts are
connected to the camp-net.
In these environments, we have tested many types of SOCKS5 clients,
including the SocksCap32[SOCKSCAP] on Windows and a variety of UNIX
based SOCKS libraries, and confirmed any clients successfully
connected to the IPv6 hosts using telnet, ftp, http, ssh.
Also we have tested very complicated interconnection of IPv4 and
IPv6. At the WIDE camp held in September 1998, we constructed an
IPv4 over IPv6 tunnel using the SOCKS64 and the FAITH translator. In
this system, the SOCKS5 clients had no problems connecting to the
IPv4 hosts through the IPv6 networks.
IPv4 host --SOCKS-- SOCKS64 --IPv6-- IPv6-IPv4 -- IPv4 host
/IPv4 server translator
In conclusion, SOCKS64 provides an easy and sure way to let IPv4
hosts connect to IPv6 hosts.
H. Kitamura et al. [Page 12]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
8. Conclusion
As described above, the SOCKS-based IPv6/IPv4 gateway mechanism has
many advantages. From a realistic viewpoint, constraints are
negligible.
Only two things are necessary to utilize this gateway mechanism.
1. Prepare an enhanced SOCKS sever on the dual stack node.
[see Appendix A. two implementations are available]
2. Socksify applications when you execute them.
This is a very easy procedure.
You don't have to modify the DNS system at all.
You don't have to reserve any addresses.
You don't have to prepare address mapping servers. etc.
Since the mechanism is based on relaying two "terminated"
connections, most problems of the NAT-based translator mechanisms are
eliminated.
Also, the "DNS name resolving delegation" mechanism works
effectively. It enables smooth heterogenous communications between
IPv6 and IPv4 nodes without modifying the DNS system.
9. Changes
This draft is based on [SOCKS64] and
[SOCKSTRANS].
Appendix A. Implementations
Currently, there are two independent implementations of the SOCKS-
based IPv6/IPv4 gateway mechanism. Both of them are open to the
public.
One is Fujitsu Lab.'s implementation, which is called "SOCKS64." Its
source codes are available at the following URL.
ftp://ftp.kame.net/pub/kame/misc/socks64-v10r8-19990118.tgz
The other is NEC's implementation. Its source codes are available at
the following URL.
http://www.socks.nec.com/
H. Kitamura et al. [Page 13]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
References
[SOCKS64] A. Jinzaki, S. Kobayashi, "SOCKS64: An IPv4-IPv6
intercommunication gateway using SOCKS5 protocol,"
work in progress
[SOCKSTRANS] H. Kitamura, "A SOCKS-based IPv6/IPv4 Translator
Architecture," work in progress
[SOCKSv5] Leech, M., Ganis, M., Lee, Y., Kuris, R. Koblas, D., &
Jones, L., "SOCKS Protocol V5," RFC1928, April 1996.
[SOCKS5EXT] H. Kitamura, "SOCKSv5 Protocol Extension for IPv6/IPv4
Communication Environment",
work in progress
[TRANSMECH] R. Gilligan and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 1933, April 1996.
[IPv6] S. Deering, R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification," RFC2460, December 1998.
[NATPT] G. Tsirtsis and P. Srishuresh, "Network Address
Translation - Protocol Translation (NAT-PT)",
work in progress
[CATTRANS] K. Yamamoto, M. Sumikawa, "Categorizing Translators
between IPv4 and IPv6,"
work in progress
[WIDEV6WG] WIDE Project IPv6 Working Group, "WIDE Project IPv6
Working Group Home Page", http://www.v6.wide.ad.jp/.
[SOCKSCAP] NEC, "SocksCap Home Page",
http://www.socks.nec.com/sockscap.html.
Authors' Addresses:
Hiroshi Kitamura
NEC Corporation
C&C Media Research Laboratories
1-1, Miyazaki, 4-Chome, Miyamae-ku,
Kawasaki, Kanagawa, 216-8555, JAPAN
Phone: +81 (44) 856-2123
Fax: +81 (44) 856-2230
Email: kitamura@ccm.cl.nec.co.jp
H. Kitamura et al. [Page 14]
INTERNET-DRAFT A SOCKS-based IPv6/IPv4 Gateway April 1999
Akira Jinzaki
Fujitsu Laboratories LTD.
4-1-1 Kamikodanaka, Nakahara-ku,
Kawasaki, Kanagawa, 211-8588 Japan
Phone: +81 (44) 777-1111 ex. 2-6331
Fax: +81 (44) 754-2771
Email: zinzin@flab.fujitsu.co.jp
Shinji Kobayashi
Fujitsu Laboratories LTD.
4-1-1 Kamikodanaka, Nakahara-ku,
Kawasaki, Kanagawa, 211-8588 Japan
Phone: +81 (44) 754-2627
Fax: +81 (44) 754-2771
Email: koba@flab.fujitsu.co.jp
H. Kitamura et al. [Page 15]